1. Field of the Invention
This invention relates generally to large bags of fabric used to transport and store granular or loose flowable material, and more specifically to flexible intermediate bulk containers having a cubic configuration wherein vertically extending baffles are provided in the interior corners of the bags to permit the bags to better retain their cubic configuration and to improve stability when filled.
2. Background Art
The use of large bags of fabric, commonly called flexible, intermediate bulk containers (FIBCs) or simply bulk bags, has become commonplace for transporting bulk quantities of powdered or granular materials. Bulk bags can be lifted and moved by forklift trucks and other material handling equipment having hooks or tines. The cloth for the bulk bags is usually woven of strong, tape-like man-made plastic fibers (e.g., polypropylene), though natural fibers could be employed. Flexible intermediate bulk containers have come into widespread use for receiving, storing, transporting, and discharging flowable materials of all types, including for example liquids.
Although circular bulk bags are known, bulk bags are often constructed from rectangular panels which are sewn together along their adjacent edges to define a bulk bag which initially has a horizontally square or rectangular cross section, as is shown in bulk bag 210 of FIG. 2. When the bulk bag 210 is filled, the nominal shape of the bag configuration, whether rectangular, square or circular, is achieved. For rectangular-sided bags 210, the bag assumes a cubic or rectangularly shaped figure, as shown. This shape is preferable to a circular shape because stacking of the bags becomes a significantly better and more efficient use of space in that voids between the corners 214 of the bags 210 are minimized. However, bulk bags 210, regardless of whether they have a square, rectangular, or circular cross-section, tend to bulge out at the sidewalls 222 (FIG. 2) when filled due to the outwardly directed pressure imposed by the weight of the lose granular and flowable bulk bag contents pressing against the flexible fabric sidewalls 222.
Bulk bags bulging in the center of the sidewalls lead to problems when filled bags are placed side by side. More space becomes necessary between bags with bulging sidewalls than between bags that have planar sidewalls and square corners. The problem is increasingly pronounced when bags are stacked vertically as the weight of the added stacked bags compresses the material in the bags below adding to the internal outward pressure of the material in the bags. Various methods have been considered to address the bulging bags, including use of baffles for providing additional lateral support to the corners of bags when the bags are filled thereby inhibiting tension at the central portions of the sidewalls, and thereby reducing bulging.
For example, U.S. Pat. No. 4,903,859 discloses a bulk bag comprising four double layer sidewalls attached to each other at their boundaries. Stiffeners formed from cardboard are inserted between the layers of the sidewalls thereby imparting sufficient rigidity to the container to permit its use with liquids. Although bulk bags made according to the '859 patent have been in use for some time, their use has been somewhat limited by the challenges encountered in stacking the bags.
U.S. Pat. No. 5,076,710 discloses a baffle-type bulk bag 210, as shown in FIG. 2, wherein bridge panels or baffles 212 are sewn across the four corners 214 of a nominally rectangular bulk bag. The baffles 212 reduce the bulging of the sidewalls 222 outwardly when the bulk bag is filled, thereby retaining the filled bulk bag 210 in a more or less rectangular cross-sectional configuration. The baffles have cut-out apertures 218 which allow loose granular material to flow into and out of the corners 214 of the bulk bag 210 during filling and discharging operations. However, as described below, the type and size of apertures 218, and the lack of reinforcing fabric in the apertures 218, rather than just between the apertures 218 at the fabric web 220, do not provide for as strong a web of fabric in the baffles 212 at the corners 214. This results in the formation of bulges and waves on the side wall surfaces 222 of the bulk bags 210 because of the uneven tension when viewed in the horizontal direction horizontally across the baffle webs 220 caused by the aperture cut-outs 212. The result can be seen in the shape of bulk bags 210 as shown in the perspective view of FIG. 4, whereupon after filling of the bags 210, the sidewalls 222 produce bulges 224 at the vertical positions where the baffles 212 have an aperture 218 and produce undulating indentations 226 at those vertical positions along the bag walls 214 which are adjacent the web portions of the baffle 212.
U.S. Pat. No. 5,468,528 describes a FIBC with baffles having triangular apertures. The corner, baffle and sidewalls are connected to each other along the vertical edges of the baffle. This construction is stated as providing a more efficient stitching operation for when a plastic or polyethylene liner is provided internally in the bag inner walls to seal the interior from moisture and other unwanted contaminants. However, the configuration adds to the complexity of manufacturing processes and diminishes the available uninterrupted side wall surface on the bags for the stencilling of company names or other identifying information or other means of identification on the bag sidewalls.
U.S. Pat. No. 5,564,833 discloses a lined bulk bag, i.e., a FIBC, having sidewalls of a flexible material and baffles across the corners to maintain a square configuration. The liner baffles are claimed to impart a “square” configuration to the FIBC. The liner is described as being a polyolefin sheet material baffle-type bulk bag wherein bridge panels or baffles are sewn across the four corners of a nominally rectangular bulk bag. The liner is disclosed as being impervious to air and moisture. The lined bulk bag disclosed in this patent includes apertures having diamond shapes with an apex of the diamond in a lowermost position.
In U.S. Pat. No. 6,283,470, a baffle-type bulk bag is described having reinforcing triangular stiffener supporting members positioned in the corners of the bulk bag to provide lateral support and to facilitate stacking of formed bulk bags. The stiffeners may be formed from various materials including plastic panels, panels formed from corrugated paperboard and similar materials, etc. The stiffeners may be provided with apertures aligned with the apertures of the baffles thereby permitting the flow of material into and out of the bulk bag during filling and discharging operations. The stiffener inserts are not flexible, being made of rigid plastic, so that the bags do not completely collapse when empty, making transport of unfilled bags cumbersome.
Other baffle style bags are described in U.S. Pat. Nos. 5,203,633; 5,468,528; 6,015,057; 6,220,755; and 7,794,148, each of which provide for different mechanisms or designs that attempt to solve the problem of bulging bags. However, for the most part those designs that utilize baffles create a new problem in impairing the filling and discharging of dry or granular material from the corners of the bulk bags. Prior to the present invention, bulk bags without large apertures were used for ease of transport and storage of dry, loose granular material. One example of these bags 110 are shown in a perspective view in FIG. 1. Bulk bags 110 are typically shipped on pallets 120, and include loops 112 adjacent an upper surface 114, the loops 112 being used for ease in moving the bags 110 to and from different storage and transport locations. The bulging sidewalls 116 are evident in bag 110 of FIG. 1, since no lateral side supports are present to distribute the load on the flat bag sidewall panels 116. When the bags are stacked (not shown) the sidewalls 116 of bulging bags 110 result in fewer bags being able to be stored in the same amount of space, in that the bulging sides walls 116 will require more distance between bag centers because the bulging sides create a larger “footprint” taking up more floor space because of the gaps created between the sidewalls of adjacent bags. Moreover, these types of bags were susceptible to shifting and internal movement of the contents during shipment, leading to instability in the bag configuration.
Bulk bags with configurations that use baffles with large apertures, as shown in two additional prior art bags 210, 310 in FIGS. 2 and 3, however, produce a different set of problems. Use of baffles 212, 312 with large apertures 218, 318 cannot provide uniform lateral support to the sidewalls 222, 322, thereby causing undulations 224, 226 in the sidewalls 222 of filled bags 210, as can be seen in bulk bag 210 shown in the perspective view of FIG. 4. Most of these apertures 218, 318 have width and length dimensions that result in large open areas between the strips 212, 312 of the fabric web that comprise the baffle elements, the width and length dimensions being determined by the necessity to efficiently move the material into and out of the bag corners 214, 314, defined by adjoining walls 222, 322, during filling and discharge.
Removal of the material from between the apertures 218, 318 decreases the ability to control the tension provided to the bag structure by the baffles 212, 312 and provides corners 214, 314 resulting from the baffle structures 212, 312 that do not fully isolate the bag contents in the corners 214, 314. Specifically, since the tension is concentrated in the strips 212, 312 of the baffle web, that is, between the cut-outs or apertures, 218, 318, there is no tension or other horizontal or lateral structural support that can be provided by the structure at the position of the cut-outs 218, 318 at the specific points where the web fabric of baffles 212, 312 is attached to the sidewalls 222, 322. This results in undulations from the indents 224 (FIG. 4) at the places where there are strips in 212, and protuberances 226, where there are apertures 218, in the sidewalls 222 of the bags 210 (FIG. 4) due to the uneven tension on the sidewalls 222 provided by the baffles 212, 312. That is, uneven tension is directed at the places where the sides of baffles 212 are attached to the sidewalls 222, and that tension is directed to discrete areas of the sidewalls 222 that are being pulled together by strips 212 while adjacent areas including the cut-outs or apertures 218 are providing the uneven lateral support. Uneven tension makes for weaker bags since there is a greater force continuously being applied to the sides of the bags. Additionally, if the filled bags are being shipped or transported, shifting of the material in the bags 210 caused by movement of the bags can increase or decrease the amount of tension on the sidewalls provided by the large apertures in baffles 212, 312 thereby providing uneven tension which over time weakens the sidewalls 222. At the top of the corner 214 adjacent the loop 208, there may develop a loose or turned over portion 228 due to the lack of material in the upper part 117 of the corner that leads to a less than square appearance. Moreover, large apertures 218, 318 provide large openings which fail to inhibit internal shifting of the loose granular contents during shipment between the corner volume and the interior volume.
Referring again to FIG. 4, the undulations caused by the troughs 226 and protuberances 224 cause large wrinkles in the sidewalls 222, as shown, that give a less than neat appearance to logos, company names, trademarks and labels that are stencilled or affixed to the outer surfaces of sidewalls 222, 322 of the bags, and make the bags less appealing to customers. The unseemly appearance of such bags makes them less desirable to the recipients of the filled bags, and thus also less desirable to the customers of the bag manufacturers.
U.S. Pat. No. 5,873,655 appears to recognize the problem caused by large apertures in baffles. It discloses the use of spaced apart parallel strips of fabric 312 across the corners 314 of a bulk bag 310 as shown in FIG. 3. The spaces between parallel strips permit granular materials to flow into the corners 314 of the bags 310. However, it appears that the bulk bags disclosed by U.S. Pat. No. 5,873,655 have not been successful in the marketplace because of the complexity and added steps required by adding separate strips which need to be sewn into the walls defining the bag corers. Additionally, it is likely that the bags of U.S. Pat. No. 5,873,655 still suffer from the problems of uneven tension at the apertures the use of strips 312 since their use does not solve the uneven tension problem, as described above. Also, it is likely that the bags of U.S. Pat. No. 5,873,655 probably cost more to produce due to the cost of joining many strips to the bag sidewalls.